A single planar solid oxide fuel cell (SOFC) may consist of a solid electrolyte which has high oxygen ion conductivity, such as yttria stabilized zirconia (YSZ); a cathode material such as strontium-doped lanthanum manganite on one side of the electrolyte, which may be in contact with an oxidizing flow stream such as air; an anode material such as a cermet of nickel and YSZ on the opposing side of the electrolyte, which may be in contact with a fuel flow stream containing hydrogen, carbon monoxide, a gaseous hydrocarbon fuel. The flow channels containing electrically conductive interconnect plates are located on the exposed sides of the anode and cathode to provide the electrical connection between adjacent cells, and provide flow paths for the reactant (e.g., fuel and air) flow streams to contact the anode and cathode. Fuel cells may be combined into units called “stacks” in which the fuel cells may be electrically connected in series and separated by electrically conductive interconnects, such as gas separator plates which may function as interconnects. Glass seals are located between each cell and adjacent interconnects in the stack to keep the stack together and to keep fuel and air flows separate.
Fuel cells may be combined to form a stack in a linear array (configured horizontally or vertically) in which the component fuel cells may be electrically connected in series to obtain a higher voltage (as compared to the voltage output of a single cell). A fuel cell stack may contain conductive end plates on its ends. A generalization of a fuel cell stack may be the so-called fuel cell segment or column, which may contain one or more fuel cell stacks connected in series (e.g., where the end plate of one stack is connected electrically to an end plate of the next stack). A fuel cell segment or column may contain electrical leads which output the direct current from the segment or column to a power conditioning system. A fuel cell system may include one or more fuel cell columns, each of which may contain one or more fuel cell stacks, such as solid oxide fuel cell stacks.